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Updated: Jan 29, 2026

The Citrobacter rodentium Mouse Model: Studying Pathogen and Host Contributions to Infectious Colitis
Published on: February 19, 2013
Macrophage β2-Integrins Regulate IL-22 by ILC3s and Protect from Lethal Citrobacter rodentium-Induced Colitis
Baomei Wang1, Jong-Hyung Lim1, Tetsuhiro Kajikawa1
1Department of Microbiology, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104, USA.
Abstract:
β2-integrins promote neutrophil recruitment to infected tissues and are crucial for host defense. Neutrophil recruitment is defective in leukocyte adhesion deficiency type-1 (LAD1), a condition caused by mutations in the CD18 (β2-integrin) gene. Using a model of Citrobacter rodentium (CR)-induced colitis, we show that CD18-/- mice display increased intestinal damage and systemic bacterial burden, compared to littermate controls, ultimately succumbing to infection. This phenotype is not attributed to defective neutrophil recruitment, as it is shared by CXCR2-/- mice that survive CR infection. CR-infected CD18-/- mice feature prominent upregulation of IL-17 and downregulation of IL-22. Exogenous IL-22 administration, but not endogenous IL-17 neutralization, protects CD18-/- mice from lethal colitis. β2-integrin expression on macrophages is mechanistically linked to Rac1/ROS-mediated induction of noncanonical-NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome-dependent IL-1β production, which promotes ILC3-derived IL-22. Therefore, β2-integrins are required for protective IL-1β-dependent IL-22 responses in colitis, and the identified mechanism may underlie the association of human LAD1 with colitis.
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